The present invention relates to a method for the treatment of water contaminated by thermal oil and collection of the thermal oil, after being accidentally discharged in water. An example of thermal oil would be that used in solar thermal elements as a heat transmission medium (Heat Transfer Fluid, HTF).
It is applicable in the renewable energies and industrial water treatment industries.
Thermal oil is normally used at solar thermal power plants as a heat transmitter, constituting the fluid used to transfer the heat captured from solar radiation by means of parabolic cylinders.
Accidental spills of thermal oil on floors or in water at a solar thermal power plant are inevitable in many cases, constituting an environmental and health and safety problem for workers. At many power plants, water contaminated by thermal oil is currently evacuated by means of an unauthorised management company, since it is hazardous waste. The cost of this removal is high and in no case does the solar thermal power plant collect the spilled thermal oil, with the added economic loss entailed.
However, if it is not removed by means of an authorised management company, different water treatment techniques can be applied:                Treatment using active carbon filters: this technique does not collect the thermal oil and adapts poorly to changes in the concentration of the pollutant, due to being difficult to plan the time the contaminated water is retained in the filter. Additionally, the filter may be prematurely saturated as a result of the adsorption of the undiluted thermal oil. The effectiveness of the filter is not optimised.        Treatment using grease separators: it is very difficult to collect the thermal oil using this technique. It is not used to collect oil. In many cases, the contaminated water is finally diluted so that the outflow parameters fulfil the standard. It does not have optimum results.        Coalescent filters, membranes, etc.: on their own they have poor results, due to which they are usually supplemented by active carbon filters. Likewise, it is difficult to collect the thermal oil using them.        
An example of used thermal oil would be a eutectic mixture of biphenyl (C12H10) and diphenyl oxide (C12H10O), which adopts different states in water depending on the temperature thereof. This thermal oil is highly toxic to aquatic organisms and can have long-term negative effects on the environment. Likewise, it irritates the airways and skin, and its decomposition can generate traces of benzene and phenol, which are also toxic.
Therefore, the oil must be prevented from reaching the environment.
The applicant is not aware of any solution that enables the efficient collection of the thermal oil in the contaminated water treatment process using said solution. Neither is the applicant aware of an optimised treatment process for water contaminated with thermal oil.